For me, it's not so much the leaves or the trees themselves but taking a moment out of my day just to sit there and do nothing. It's a form of meditation. The leaves, trees, waves, etc... are just there as a sort of visualization for your moment, and usually you'll notice things about them that you normally don't. Just because my time is valuable doesn't mean I'm going to make sure I spend every minute of my time as efficiently as possible. Sometimes I just need to sit on the beach and watch the waves crash. Or sit on a park bench and watch the people walking around.